Flexible actuator and joint-driving unit using the same

ABSTRACT

A displacement member can be displaced in a direction substantially perpendicular to a moving direction of a translation member that is held on a base member so as to reciprocatingly move thereon linearly, and an elastic mechanism secured to the base member accumulates and releases elastic energy in accordance with the distance to the displacement member. Protruding members of the translation member are pressed against a transmission member by generated force provided by the energy release from the elastic mechanism; thus, a distance adjusting operation between coupling mechanisms coupling the transmission member and the displacement member is controlled by a control device so that the relative position and relative angle between the displacement member and the transmission member are changed.

TECHNICAL FIELD

The present invention relates to a flexible actuator with which forcecontrol is easily carried out with superior operation efficiency, and ajoint-driving unit using the actuator.

BACKGROUND ART

In recent years, there are high expectations for robots that areoperated within areas close to people, such as robots for medicalapplications, domestic robots, and work support robots for use infactories. Unlike industrial robots, it is important for these robots toensure safety when the robots are in contact with a person. In order toreduce impact upon contact, for the necessity to reduce a force to acton the contact point, the torque in the joint needs to be controlled toprovide a flexible joint when viewed from the robot arm side. However,in the force (torque) control using an actuator for driving the joint,it is not possible to increase the response frequency infinitely, and inthe case where force in a high-frequency range is exerted, such as inthe case where a robot arm collides with a person, it is not possible todeal with the force. Normally, a combination of a motor and a speedreducer is used for joint driving, and when viewed from the robot armside, the inertia is represented by a value obtained by multiplying theinertia inherent to the motor by the square of the reduction ratio. Forthis reason, in a state where force control is not effective, extremelylarge force acts on the contact point, with the result that it is notpossible to sufficiently ensure safety by using only the force control.

In view of these issues, a system has been proposed in which an actuatorand a load are connected to each other through an elastic memberreferred to as “Series elastic actuators (SEA)” (for example, see PatentDocument 1). The SEA makes it possible to suppress even force in ahigh-frequency range that cannot be controlled by actuators, byutilizing flexibility of the elastic member, and also provides aflexible actuator that can achieve a flexible joint at all times whenviewed from the arm side, so that it becomes possible to ensure highersafety. On the other hand, since the SEA is connected to a load throughan elastic member, its controllable frequency bands are lowered incomparison with a conventional device. In order to compensate for thesedisadvantages, there has been proposed another system, such as a systemreferred to as “Distributed macro-mini actuation (DM2)” that isadditionally provided with an actuator for high frequencies (forexample, see Non-Patent Document 1), or a system referred to as“Variable Stiffness Transmission (VST)” in which the rigidity of theelastic member is variably controlled (for example, see Non-PatentDocument 2).

-   Patent Document 1: U.S. Pat. No. 5,650,704-   Non-Patent Document 1: IEEE Robotics & Automation Magazine, Volume    11, Issue 2, pages 12 to 21-   Non-Patent Document 2: IEEE Robotics & Automation Magazine, Volume    11, Issue 2, pages 22 to 33

DISCLOSURE OF INVENTION Subject to be Solved by the Invention

In the above-mentioned flexible actuators, such as SEA, DM2, and VST, inan attempt to greatly reduce influences of the inertia on the motor siderelative to an input from the robot arm side, the robot arm and themotor are connected to each other through an elastic member. From theopposite point of view, this system fails to transmit energy inputtedfrom the robot arm side directly to the motor side, making it difficultto electrically regenerate the energy. In the case of a robot that isoperated within an area close to people, there are many opportunities inwhich a work is done from the outside of the flexible actuator, such asin a cooperative operation with a person or in an operation for bringingan object down. However, in the case of a conventional flexible actuatorthat fails to regenerate energy, even in a state where a work is donefrom the outside of the flexible actuator, energy is consumed on theactuator side to cause an issue that the efficiency is greatly loweredthroughout the entire operation.

In view of these issues, an object of the present invention is toprovide a flexible actuator with which force control is easily carriedout with superior operation efficiency, and a joint-driving unit usingthe actuator.

Means for Solving the Subject

In order to achieve the above-mentioned object, the present inventionhas the following arrangement.

According to a first aspect of the present invention, there is provideda flexible actuator capable of carrying out a translation operation,comprising:

a base member;

a translation member that is held on the base member so as to movereciprocatingly thereon linearly;

a displacement member that is capable of being displaced in a directionsubstantially perpendicular to a moving direction of the translationmember;

an elastic mechanism that is secured to the base member, foraccumulating and releasing elastic energy in accordance with a distanceto the displacement member;

a transmission member that is connected to the displacement member so asto allow the distance relative to the displacement member to be adjustedby two or more coupling mechanisms;

a protruding member that is formed on the translation member in aprotruding manner to be pressed against the transmission member by forcegenerated by energy released from the elastic mechanism; and

a control device for changing a relative position and a relative anglebetween the displacement member and the transmission member bycontrolling an adjusting operation of the distance relative to thecoupling mechanisms.

According to a second aspect of the present invention, there is provideda flexible actuator capable of carrying out a swinging operation and arotating operation, comprising:

a base member;

a rotating member that is held on the base member so as to rotate freelythereon;

a displacement member that is capable of being displaced in a directionthat is substantially same as a rotation shaft direction of the rotatingmember;

an elastic mechanism that is secured to the base member, foraccumulating and releasing elastic energy in accordance with a distanceto the displacement member;

a transmission member that is connected to the displacement member so asto allow the distance relative to the displacement member to be adjustedby three or more coupling mechanisms;

a protruding member that is provided on the rotating member at aposition off a rotation center of the rotating member in a protrudingmanner to be pressed against the transmission member by force generatedby energy released from the elastic mechanism; and

a control device for changing a relative position and a relative anglebetween the displacement member and the transmission member bycontrolling an adjusting operation of the distance relative to thecoupling mechanisms.

In accordance with a ninth aspect of the present invention, ajoint-driving unit that is driven by the flexible actuator defined inany one of the first to eighth aspects is provided.

Effects of the Invention

In accordance with the present invention, it is possible to obtain theflexible actuator that is superior in operation efficiency and thejoint-driving unit using the actuator. That is, in accordance with thepresent invention, the force generated through the energy release fromthe elastic mechanism is outputted to the translation member at a speedvariably changed in response to the amount of inclination of thetransmission member, so that force control can be easily carried out bycontrolling the amount of inclination of the transmission member, and itis possible to obtain the flexible actuator with which even uponapplication of force in a high-frequency range, the generated force isregulated by the elasticity of the elastic mechanism, and the presentinvention also provides the joint-driving unit using the actuator.Further, the displacement of the translation member varies incooperation with the displacement of the elastic mechanism; therefore,when a work is done from the outside of the actuator, the energyinputted to the actuator is accumulated in the elastic mechanism, sothat it is possible to improve the operation efficiency.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1A is a perspective view schematically showing a translationactuator in accordance with a first embodiment of the present invention;

FIG. 1B is a cross-sectional view taken along line X-X of FIG. 1A,schematically showing the translation actuator in accordance with thefirst embodiment of the present invention;

FIG. 1C is a cross-sectional view taken along line Y-Y of FIG. 1B,schematically showing the translation actuator in accordance with thefirst embodiment of the present invention;

FIG. 1D is a cross-sectional view taken along line X-X of FIG. 1A,schematically showing the translation actuator at the time of driving inaccordance with the first embodiment of the present invention;

FIG. 1E is a cross-sectional view taken along line A-A of FIG. 1B,schematically showing the translation actuator in accordance with thefirst embodiment of the present invention;

FIG. 2A is a cross-sectional view schematically showing a rotatingactuator in accordance with a second embodiment of the presentinvention;

FIG. 2B is a top view schematically showing the rotating actuator inaccordance with the second embodiment of the present invention;

FIG. 2C is a cross-sectional view taken along line A-A of FIG. 2A,schematically showing the rotating actuator in accordance with thesecond embodiment of the present invention;

FIG. 2D is a cross-sectional view schematically showing the rotatingactuator at the time of driving in accordance with the second embodimentof the present invention;

FIG. 2E is a cross-sectional view schematically showing a differentstructural example of a rotating actuator as a modification of thesecond embodiment of the present invention;

FIG. 2F is an enlarged view showing the vicinity of a transmission plateof FIG. 2A in the rotating actuator in accordance with the secondembodiment of the present invention;

FIG. 3A is a cross-sectional view schematically showing a rotatingactuator in accordance with a third embodiment of the present invention;

FIG. 3B is a cross-sectional view taken along line A-A of FIG. 3A,schematically showing the rotating actuator in accordance with the thirdembodiment of the present invention;

FIG. 3C is a cross-sectional view schematically showing the rotatingactuator at the time of driving in accordance with the third embodimentof the present invention;

FIG. 4 is a perspective view schematically showing a joint-driving unitthat uses the translation actuator in accordance with the firstembodiment of the present invention;

FIG. 5A is a front view schematically showing the joint-driving unitthat uses the translation actuator in accordance with the firstembodiment of the present invention;

FIG. 5B is a front view schematically showing the joint-driving unitthat uses the translation actuator in accordance with the firstembodiment of the present invention;

FIG. 6 is a perspective view schematically showing a joint-driving unitthat uses the rotating actuator in accordance with the second embodimentof the present invention;

FIG. 7A is a side view schematically showing the joint-driving unit thatuses the rotating actuator in accordance with the second embodiment ofthe present invention; and

FIG. 7B is a side view schematically showing the joint-driving unit thatuses the rotating actuator in accordance with the second embodiment ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments in accordance with the present invention will be describedbelow in detail with reference to the drawings.

Prior to the detailed description of the embodiments of the presentinvention with reference to the drawings, various modes of the presentinvention will be described below.

According to a first aspect of the present invention, there is provideda flexible actuator capable of carrying out a translation operation,comprising:

a base member;

a translation member that is held on the base member so as to movereciprocatingly thereon linearly;

a displacement member that is capable of being displaced in a directionsubstantially perpendicular to a moving direction of the translationmember;

an elastic mechanism that is secured to the base member, foraccumulating and releasing elastic energy in accordance with a distanceto the displacement member;

a transmission member that is connected to the displacement member so asto allow the distance relative to the displacement member to be adjustedby two or more coupling mechanisms;

a protruding member that is formed on the translation member in aprotruding manner to be pressed against the transmission member by forcegenerated by energy released from the elastic mechanism; and

a control device for changing a relative position and a relative anglebetween the displacement member and the transmission member bycontrolling an adjusting operation of the distance relative to thecoupling mechanisms.

In accordance with this arrangement, since the generated force in theelastic mechanism is outputted to the translation member at a speedvariably changed in accordance with the amount of inclination of thetransmission member, force control can be easily carried out bycontrolling the amount of inclination of the transmission member, and itis possible to obtain the flexible actuator with which, even uponapplication of force in a high-frequency range, the generated force isregulated by the elasticity of the elastic mechanism. Further, thedisplacement of the translation member varies in cooperation with thedisplacement of the elastic mechanism; therefore, when a work is donefrom the outside of the flexible actuator, the energy inputted to theactuator is accumulated in the elastic mechanism, so that it is possibleto improve the operation efficiency. Therefore, the flexible actuatorthat is superior in operation efficiency can be obtained.

According to a second aspect of the present invention, there is provideda flexible actuator capable of carrying out a swinging operation and arotating operation, comprising:

a base member;

a rotating member that is held on the base member so as to rotate freelythereon;

a displacement member that is capable of being displaced in a directionthat is substantially same as a rotation shaft direction of the rotatingmember;

an elastic mechanism that is secured to the base member, foraccumulating and releasing elastic energy in accordance with a distanceto the displacement member;

a transmission member that is connected to the displacement member so asto allow the distance relative to the displacement member to be adjustedby three or more coupling mechanisms;

a protruding member that is provided on the rotating member at aposition off a rotation center of the rotating member in a protrudingmanner to be pressed against the transmission member by force generatedby energy released from the elastic mechanism; and

a control device for changing a relative position and a relative anglebetween the displacement member and the transmission member bycontrolling an adjusting operation of the distance relative to thecoupling mechanisms.

In accordance with this arrangement, since the generated force in theelastic mechanism is outputted to the rotating member at a speedvariably changed in accordance with the amount of inclination of thetransmission member, torque control can be easily carried out bycontrolling the amount of inclination of the transmission member, and itis possible to obtain the flexible actuator with which, even uponapplication of force in a high-frequency range, the generated force isregulated by the elasticity of the elastic mechanism. Further, therotation of the rotating member occurs in conjunction with thedisplacement of the elastic mechanism; therefore, when a work is donefrom the outside of the flexible actuator, the energy inputted to theactuator is accumulated in the elastic mechanism, so that it is possibleto improve the operation efficiency. Therefore, the flexible actuatorthat is superior in operation efficiency can be obtained.

According to a third aspect of the present invention, there is providedthe flexible actuator according to the second aspect, wherein thecoupling mechanisms are circumferentially disposed at equal intervals.

With this arrangement, variation in controllability due to angles of therotating member can be minimized, and it is possible to provide theflexible actuator that is superior in controllability.

According to a fourth aspect of the present invention, there is providedthe flexible actuator according to any one of the second to thirdaspects, wherein a contact point between the protruding member and thetransmission member is located substantially on same plane as a sideface of an elliptic column that includes a contact point between thecoupling mechanisms and the transmission member or a rotation center ofa coupling portion therebetween and has a height in a displacementdirection of the displacement member.

With this arrangement, it is possible to reduce the amount of work ofthe coupling mechanisms required for inclining the transmission memberin the radial direction of the rotating member, centered on the contactpoint between the protruding member and the transmission member.Therefore, the flexible actuator with higher operation efficiency can beobtained.

According to a fifth aspect of the present invention, there is providedthe flexible actuator according to any one of the first to fourthaspects, wherein a contact point between the protruding member and thetransmission member is located substantially on same plane as a sideface of an elliptic column that includes a contact point between thecoupling mechanisms and the transmission member or a rotation center ofa coupling portion therebetween and has a height in a displacementdirection of the displacement member.

With this arrangement, it is possible to reduce the amount of work ofthe coupling mechanisms required for inclining the transmission memberin the moving direction of the protruding member, centered on thecontact point between the protruding member and the transmission member.Therefore, the flexible actuator with higher operation efficiency can beobtained.

According to a sixth aspect of the present invention, there is providedthe flexible actuator according to any one of the first to fifthaspects, wherein the elastic mechanism is a ram-type cylinder or asingle rod cylinder that allows a fluid to move between pressurechambers on two sides of a piston.

With this arrangement, since changes in the generated force of theelastic mechanism due to changes in the distance to the displacementmember are reduced, the flexible actuator with which force control iseasily carried out can be obtained.

According to a seventh aspect of the present invention, there isprovided the flexible actuator according to any one of the first tosixth aspects, wherein the coupling mechanisms have a structure withwhich the distance between the displacement member and the transmissionmember is adjustable substantially in parallel with a displacementdirection of the displacement member and which is pressed against thetransmission member by generated force of the elastic mechanism.

With this arrangement, since the hold of the coupling mechanisms areenhanced by taking into consideration only movements having one degreeof freedom, hold with high rigidity becomes easily possible. Therefore,since unnecessary movements that give adverse effects on thecontrollability are reduced, it is possible to obtain the flexibleactuator with which force control is easily carried out.

According to an eighth aspect of the present invention, there isprovided the flexible actuator according to any one of the first tosixth aspects, wherein the coupling mechanisms are coupled to thedisplacement member and the transmission member respectively so as torotate freely thereon, is variably adjustable a distance between bothconnecting points thereof.

With this arrangement, since the coupling mechanisms become able togenerate not only force in an expanding direction but also force in acontracting direction relative to the transmission member, position andangle controls of the transmission member by using the expanding andcontracting operations of the coupling mechanisms can be easily carriedout. Therefore, it is possible to obtain the flexible actuator withwhich force control is more easily carried out.

In accordance with the ninth aspect of the present invention, there isprovided a joint-driving unit that is driven by the flexible actuatordefined in any one of the first to eighth aspects.

With this arrangement, since the joint-driving unit that is driven bythe flexible actuator described in any one of the first to eighthaspects is constructed, it is possible to obtain the joint-driving unitthat has the functions and effects of the above-mentioned flexibleactuator.

Various embodiments of the present invention will be described below indetail with reference to the drawings.

First Embodiment

FIG. 1A is a perspective view schematically showing a translationactuator 1 serving as one example of a flexible actuator in accordancewith a first embodiment of the present invention, FIG. 1B is across-sectional view taken along line X-X of FIG. 1A, and FIG. 1C is across-sectional view taken along line Y-Y of FIG. 1B. Moreover, FIG. 1Eis a cross-sectional view taken along line A-A of FIG. 1B. In FIGS. 1Ato 1C, a frame 12 a which has an elongated rectangular parallelepipedbox shape along a vertical direction serves as one example of a basemember. A pair of guide rails 13 a and 13 b in parallel with each otherare secured to the inside of the upper face of the frame 12 a in such amanner as to extend in a lateral direction orthogonal to the verticaldirection. A plate-shaped translation member 11 is connected to theguide rails 13 a and 13 b in such a manner as to freely movereciprocally in a lateral direction in FIG. 1B (to freely move rightwardand leftward). The linear guide rails 13 a and 13 b are fitted to a pairof guide grooves 11 g in parallel with each other on the upper face ofthe translation member 11 in such a manner as to freely slide thereinand are guided along the lateral direction so as to reciprocally movelinearly. On the front and rear side faces on an upper portion of theframe 12 a, a through hole 12 p that allows the translation member 11 tofreely come into and go out is formed. Moreover, on the lower face ofthe translation member 11, the upper ends of rod-shaped protrusions 14 aand 14 b that serve as an example of protruding members and are extendeddownward are secured at positions that are symmetrical with each otherrelative to the center in the width direction, and semi-sphericalportions on the lower ends of the rod-shaped protrusions 14 a and 14 bare made in contact with the upper face of a transmission plate 15 ahaving a quadrilateral plate shape (for example, a square), which servesas one example of the transmission member, so as to roll thereon. Thetransmission plate 15 a has a structure in which a plate face isdisposed in a direction orthogonal to the vertical direction, with itscenter portion 15 p having recessed shapes with steps relative to thetwo end portions 15 q in a width direction orthogonal to a movingdirection of the translation member 11, so that the semi-sphericalportions on the lower ends of the rod-shaped protrusions 14 a and 14 bare made in contact with the upper face of the center portion 15 p so asto roll thereon. As will be described later, the upper face of thecenter portion 15 p of the transmission plate 15 a and the lower facesof the two end portions 15 q are formed so as to be located on the sameplane (substantially on the same plane). This transmission plate 15 aalso functions as one example of a swinging plate or a swinging member.

An elongated through hole 11 p is formed at the center of thetranslation member 11 along the moving direction of the translationmember 11 so that the movement of the translation member 11 is notintervened by a supporting rod 16, which will be described below.

The upper end of the supporting rod 16 is secured to the center of theinner face of the top face of the frame 12 a, and the supporting rod 16is disposed to extend downward from the top face of the frame 12 a andpasses through the through hole lip at the center of the translationmember 11. On an outer peripheral face of a middle portion of thissupporting rod 16, an outer cylinder 26 a is held so as to freely moveonly in the vertical direction in FIG. 1B. The transmission plate 15 ais held on the outer cylinder 26 a by a shaft so as to freely rotatearound the axis perpendicular to the paper plane of FIG. 1B.

Meanwhile, a gas cylinder 17 serving as one example of an elasticmechanism is secured onto the bottom face of the frame 12 a along thevertical direction. The gas cylinder 17 has a structure for storing ahigh-pressure gas therein and holds a ram-type piston 18 so as to movein the vertical direction in FIG. 1B. A force corresponding to a productof the cross-sectional area of the piston 18 and the pressure of thehigh-pressure gas (hereinafter, referred to as “generated force”) isapplied to the piston 18 in an upward direction in FIG. 1B. Moreover, tothe tip of the piston 18 is connected a plate member 19 a having aquadrilateral shape (for example, rectangular shape), which serves asone example of a displacement member capable of changing its position ina direction substantially perpendicular to the moving direction of thetranslation member 11, with its plate face being disposed in a directionorthogonal to the vertical direction. To the plate member 19 a, ten ballscrew nuts 20 a to 20 j are secured in two rows. More specifically, eachof the groups of the ball screw nuts 20 a to 20 e and the ball screwnuts 20 f to 20 j forms one row with the same intervals provided intherebetween, and the rows are disposed at positions that are linearlysymmetrical with each other relative to the center line of the platemember 19 a. The ball screw nuts 20 a to 20 j are respectively coupledto ten ball screw mechanisms 21 a to 21 j, each serving as one exampleof a coupling mechanism. In FIG. 1B, only the ball screw nuts 20 a to 20e and the ball screw mechanisms 21 a to 21 e are illustrated. In FIG.1B, the ball screw nuts 20 f to 20 j and the ball screw mechanisms 21 fto 21 j are respectively represented as elements that are located atpositions so as to face the ball screw nuts 20 a to 20 e and the ballscrew mechanisms 21 a to 21 e. In addition, the ball screw mechanisms 21a to 21 j are respectively configured by motors 22 a to 22 j, threadedshafts 23 a to 23 j disposed in the vertical direction, and holdingmembers 24 a to 24 j disposed in the vertical direction. Moreover, themotors 22 a to 22 j are respectively secured to the holding members 24 ato 24 j, with the rotation, shafts of the motors 22 a to 22 j beingrespectively coupled to the lower ends of the threaded shafts 23 a to 23j. The threaded shafts 23 a to 23 j are respectively held by the holdingmembers 24 a to 24 j through bearing portions or the like so as tofreely rotate thereon. Moreover, the threaded shafts 23 a to 23 j arerespectively threaded with the ball screw nuts 20 a to 20 j to penetratetherethrough. With this structure, when the rotation shafts of themotors 22 a to 22 j rotate forwardly or reversely, the threaded shafts23 a to 23 j coupled to the rotation shafts of the motors 22 a to 22 jare respectively allowed to rotate forwardly or reversely. Then, thepositions of the ball screw nuts 20 a to 20 j with which the threadedshafts 23 a to 23 j are threaded are respectively shiftedreciprocatingly on the threaded shafts 23 a to 23 j along the axialdirection of the threaded shafts 23 a to 23 j (in other words, in thedownward direction). The semi-spherical portions of the upper ends ofthe threaded shafts 23 a to 23 j are made in contact with the lowerfaces of the two ends 15 q of the transmission plate 15 a so as to rollthereon.

A control computer 101 serving as one example of a control device isconnected to each of the motors 22 a to 22 j. By controlling the driveof each of the motors 22 a to 22 j by the control computer 101, therelative position and the relative angle between the plate member 19 aand the transmission plate 15 a are changed.

Moreover, the holding members 24 a to 24 j are connected to guide rails25 a to 25 j secured to the frame 12 a in the vertical direction so asto freely move in the vertical direction in FIG. 1B. With thisarrangement, each of the ball screw mechanisms 21 a to 21 j can be heldwith high rigidity, with respect to degrees of freedom except for theexpanding and contracting directions thereof (in other words, directionsin which the distance between the plate member 19 a and the transmissionplate 15 a is adjustable (allowed to expand or contract) in the movingdirections in the vertical direction of the ball screw nuts 20 a to 20j).

In the following description, functions of this translation actuator 1that are fulfilled under the control of the control computer 101 will bediscussed.

Force to be exerted on the translation member 11 of the translationactuator 1 is determined by the generated force of the gas cylinder 17and the amount of inclination of the transmission plate 15 a. That is,when the force (generated force) generated by the gas cylinder 17 isexerted upward in FIG. 1B, the force is transmitted to the piston 18,the plate member 19 a, the ball screw nuts 20 a to 20 j, the threadedshafts 23 a to 23 j of the ball screw mechanisms 21 a to 21 j, and thetransmission plate 15 a. As a result, the transmission plate 15 a ispressed against the rod-shaped protrusions 14 a and 14 b. At this time,in the case where the transmission plate 15 a is kept in the horizontalstate (kept in a direction orthogonal to the vertical direction) asshown in FIG. 1B, the generated force of the gas cylinder 17 istransmitted to the frame 12 a through the rod-shaped protrusions 14 aand 14 b, the translation member 11, the guide rails 13 a and 13 b, andthe frame 12 a, and is kept in a balanced state. On the other hand, inthe case where the transmission plate 15 a is in an inclined state fromthe horizontal state as shown in FIG. 1D (in FIG. 1D, an inclined statediagonally upward to the right, with the left edge of the transmissionplate 15 a being inclined downward while the right edge thereof beinginclined upward), a force is exerted in a lateral direction (leftward inFIG. 1D) at each of the contact points between the transmission plate 15a and the rod-shaped protrusions 14 a and 14 b. The force exerted to thetransmission plate 15 a rightward is supported by the supporting rod 16;however, the force exerted to the translation member 11 leftward isoutputted as it is. In the case of a statical state with losses due tosliding or the like being ignored, this leftward force is represented bya product of the generated force of the gas cylinder 17 and the tangentto an angular change of the transmission plate 15 a from the horizontalstate. Based upon this, by driving the motors 22 a to 22 j so as to setthe transmission plate 15 a to an inclination angle corresponding to aforce to be desirably outputted by the control computer 101, the forcecontrol of the translation actuator 1 can be carried out.

Even upon disturbance within a high-frequency band that cannot becontrolled by the control computer 101, since flexibility is maintainedby the elasticity of the gas cylinder 17, the translation actuator 1 canbe a flexible actuator that is safe against contact.

The generated force of the gas cylinder 17 is represented by a productof the cross-sectional area of the piston 18 and the pressure of thehigh-pressure gas, and although the pressure of the high-pressure gaschanges depending on the amount of insertion of the piston 18 into thecylinder 17, the amount of the change can be reduced by making the innerdiameter of the cylinder 17 larger than the diameter of the piston 18.That is, the gas cylinder in accordance with the first embodiment makesit possible to reduce a change in the generated force relative to thedisplacement of the piston 18. Moreover, another elastic mechanism, suchas a single rod cylinder 18 in which a through hole is formed on thepiston 18 so that a pressure difference between the pressure chambers onthe two sides of the piston 18 is eliminated, that provides the sameeffects as those of the gas cylinder 17 of the first embodiment, is alsodesirably used because the change in the generated force relative to thedisplacement of the piston 18 can be reduced.

Moreover, in FIG. 1D, in the case where the translation actuator 1 isprovided in such a state that the translation member 11 is movedleftward, the translation actuator 1 shall be carrying out a work to theoutside of the flexible actuator. That is, in the case where the controlcomputer 101 causes the motors 22 a to 22 j to stop from driving, as thetranslation member 11 is moved leftward, the holding members 24 a to 24j are moved upward in FIG. 1D relative to the frame 12 a along the guiderails 25 a to 25 j. Then, the plate member 19 a is allowed to moveupward in FIG. 1D through the ball screw nuts 20 a to 20 j coupled tothe threaded shafts 23 a to 23 j of the ball screw mechanisms 21 a to 21j supported by the holding members 24 a to 24 j. At this time, thetranslation actuator 1 carries out a work to the outside of thetranslation actuator 1 with potential energy that the gas cylinder 17has lost.

In contrast, in the case where the translation actuator 1 is provided insuch a state that the translation member 11 is moved rightward, thetranslation actuator 1 is in such a state as to be subjected to a workfrom the outside of the translation actuator 1. That is, in the casewhere the control computer 101 causes the motors 22 a to 22 j to standstill, as the translation member 11 is moved rightward, the holdingmembers 24 a to 24 j are moved downward in FIG. 1D relative to the frame12 a along the guide rails 25 a to 25 j. Then, the plate member 19 a isallowed to move downward in FIG. 1D through the ball screw nuts 20 a to20 j coupled to the threaded shafts 23 a to 23 j of the ball screwmechanisms 21 a to 21 j supported by the holding members 24 a to 24 j.At this time, by the work carried out on the translation actuator 1 fromthe outside of the translation actuator 1, potential energy is stored inthe gas cylinder 17.

In this manner, the translation actuator 1 not only carries out a workto the outside of the translation actuator 1 but also carries out aregeneration operation of accumulating energy in the translationactuator 1 by the work from the outside of the translation actuator 1.Therefore, in comparison with an actuator that is unable to carry outthe regeneration operation, the translation actuator 1 of the firstembodiment makes it possible to improve its operation efficiency.

Moreover, since the driving force of the translation actuator 1 iscontrolled by the amount of inclination of the transmission plate 15 a,it becomes possible to obtain high output by releasing the potentialenergy in the gas cylinder 17 in a short period of time. To replenishpotential energy in the gas cylinder 17, the ball screw mechanisms 21 ato 21 j may be operated by the control computer 101 so that the platemember 19 a is pressed down. In the case where there is a greatdifference between a peak power required of the output of thetranslation actuator 1 and an average power thereof, since replenishmentfor the potential energy released for a short period of time may becarried out taking sufficient time, the power required for the motors 22a to 22 j may be set to a low level in comparison with the peak power.Moreover, since the pressing-down operation of the plate member 19 a iscarried out by the ball screw mechanisms 21 a to 21 j under the controlof the control computer 101 in cooperation with one another, it ispossible to reduce the power required for each of the motors 22 a to 22j.

Next, in the following description, the case where the driving force ofthe translation actuator 1 is changed will be discussed. In the firstembodiment, ten ball screw mechanisms indicated by the referencenumerals 21 a to 21 j are used as the ball screw mechanism. Since thetransmission plate 15 a is pressed against the rod-shaped protrusions 14a and 14 b having fixed lengths, the transmission plate 15 a is movedwith two degrees of freedom, that is, the vertical position and theangle, relative to the supporting rod 16. For this reason, the minimumnumber of the ball screw mechanisms required is two. However, as shownin FIG. 1C, in the case where the threaded shafts 23 b and 23 g arelocated at the same positions as those of the rod-shaped protrusions 14a and 14 b, that is, at positions rightward and leftward from thesupporting rod 16, the generated force of the gas cylinder 17 can besupported by the ball screw mechanisms 21 b and 21 g having the threadedshafts 23 b and 23 g. For this reason, with the other ball screwmechanisms being not influenced by the generated force of the gascylinder 17, the angle of the transmission plate 15 a can be changedonly by the ball screw mechanisms 21 b and 21 g, so that it is possibleto change the driving force of the translation actuator 1 easily.

Moreover, in the case where only the angle of the transmission plate 15a is changed, since no positional changes are required for the ballscrew mechanisms 21 b and 21 g, it is only necessary to hold thetransmission plate 15 a. To dispose the ball screw mechanisms in such aredundant manner is desirable because the above state is obtained atmore points.

In the first embodiment, the transmission plate 15 a is formed into ashape with steps, with its center portion 15 p having recessed shapesrelative to the two end portions 15 q, and the face (upper face of thecenter portion 15 p) with which the rod-shaped protrusions 14 a and 14 bare made in contact and the face (lower face of the two end portions 15q) with which the threaded shafts 23 a to 23 j are made in contact aredesigned to be located on the same plane (substantially on the sameplane). In contrast, in the case of a transmission plate without a step,for example, when the amount of inclination of the transmission plate 15a is changed from the state shown in FIG. 1B, the distances in thevertical direction between the contact points of the transmission plate15 a with the rod-shaped protrusions 14 a and 14 b and the contactpoints of the transmission plate 15 a with the threaded shafts 23 b and23 g are changed affected by the thickness of the transmission plate.For this reason, it becomes necessary to lower the plate member 19 aaccordingly, with the result that in order to change the amount ofinclination, additional energy corresponding to the increase inpotential energy is required. Therefore, the transmission plate 15 a isformed into the shape with steps as shown in the first embodiment withthe contact points of the transmission plate 15 a with the rod-shapedprotrusions 14 a and 14 b and the contact points of the transmissionplate 15 a with the threaded shafts 23 b and 23 g being located on thesame plane (substantially on the same plane), which is desirable becausethis structure can eliminate influences of the thickness of thetransmission plate 15 a.

In the first embodiment, the ball screw mechanisms 21 a to 21 j are usedas one example of the coupling mechanism; however, the structure of thecoupling mechanism is not limited thereto, and any combination ofconventional techniques may be used as long as the same functions areachieved.

Moreover, FIG. 4 shows a structural example of the joint-driving unit inwhich the translation actuator 1 of the first embodiment is used. Anoutput transmitting member 51 having a C-shaped side face is coupled tothe translation member 11 of the translation actuator 1, and a rack 52is secured onto the output transmitting member 51. Meanwhile, a pinion53 is secured to the lower end of an arm 54 a disposed above a frame 12d and is engaged with the rack 52. Moreover, the lower end of the arm 54a and the upper end of the frame 12 d are coupled to each other througha shaft 55 so as to freely rotate thereon.

With this arrangement, when the translation actuator 1 is operated fromthe state shown in FIG. 5A so that the translation member 11 is movedrightward, the arm 54 a is allowed to rotate clockwise around the shaft55 relative to the frame 12 d through the rack 52 and the pinion 53, tobe brought into a state shown in FIG. 5B. In the same manner, when thetranslation member 11 is moved leftward, the arm 54 a is also allowed torotate in a reverse direction relative to the frame 12 d (that is,counterclockwise around the shaft 55).

By using this structure, it is thus possible to obtain a joint-drivingunit that has the features of the translation actuator 1 of beingsuperior in operational efficiency in addition to being flexible, andalso to achieve a joint-driving unit for a robot arm that isparticularly suitable for domestic applications.

The method for constructing the joint-driving unit is not limited to oneusing a rack-and-pinion mechanism, and any combination of conventionaltechniques may be used as long as the same functions are achieved.

Second Embodiment

FIG. 2A is a cross-sectional view schematically showing a rotatingactuator 2 a serving as one example of a flexible actuator in accordancewith a second embodiment of the present invention. FIG. 2B is a top viewof the rotating actuator 2 a, and FIG. 2C is a cross-sectional viewtaken along line A-A of FIG. 2A. FIG. 2F is an enlarged view showing thevicinity of a transmission plate 15 b of FIG. 2A. The portions havingthe same functions as those of the above-described first embodiment areindicated by the same reference numerals, and overlapping description isnot given. In the flexible actuator of the second embodiment, the Z-axisin the coordinate axes is defined as upward in the vertical direction.The X-axis is defined as a direction that is orthogonal to the Z-axisand penetrates one of side faces of a rectangular parallelepipedbox-shaped frame 12 b in the thickness direction, the frame 12 b servingas one example of a base member. The Y-axis is defined as a directionthat is orthogonal to the Z-axis and X-axis and penetrates a side facethat is orthogonally adjacent to the side face of the rectangularparallelepiped box-shaped frame 12 b.

In the second embodiment, the disc-shaped transmission plate 15 bserving as one example of a transmission member is used to output arotating movement, where the transmission plate 15 b corresponding tothe transmission plate 15 a of the first embodiment. The transmissionplate 15 b is held on a ring-shaped member 33 provided with a shaftportion protruding in the X-axis direction so as to freely rotate aroundthe X-axis by a bearing or the like. At the same time, the ring-shapedmember 33 is held by a supporting rod 16 serving as a spline shaftsecured downward to the center of the inner face of the upper face ofthe frame 12 a, so as to move freely reciprocatingly only in the Z-axisdirection (axial direction of the supporting rod 16), and is also heldby an outer cylinder 26 b provided with a shaft portion protruding inthe Y-axis direction, so as to rotate freely around the Y-axis, througha bearing or the like. Moreover, a bevel gear 31 serving as one exampleof a rotating member is held by the supporting rod 16 so as to freelyrotate around the Z-axis through a bearing or the like. A rod-shapedprotrusion 14 c serving as one example of a protruding member isprovided on the lower face of the bevel gear 31 at a position apart fromthe rotation center in such a manner as to extend downward therefrom, sothat its semi-spherical portion on the lower end is made in contact withthe upper face of a round center portion 15 r of the transmission plate15 b so as to roll thereon. Moreover, semi-spherical portions on theupper ends of the threaded shafts 23 a to 23 j are made in contact withthe lower face of an annular outer peripheral portion 15 s around theround center portion 15 r of the transmission plate 15 b so as to rollthereon. For the same reasons as those of the aforementioned firstembodiment, the upper face of the round center portion 15 r of thetransmission plate 15 b and the lower face of the annular outerperipheral portion 15 s are formed so as to be located on the same plane(substantially on the same plane).

Note that the transmission plate 15 b also functions as one example of aswinging plate or a swinging member.

The rotating output of the bevel gear 31 is taken out of the rotatingactuator 2 a as a forward/reverse rotating output around the Y-axis,through a rotation shaft (rotation shaft to which the bevel gear 31 issecured) 32 with the bevel gear which is held on a pair of bearingportions 12 r formed on an opening portion 12 q of the upper face of theframe 12 b serving as one example of the base member, through a bearingportion or the like so as to freely rotate thereon. A bevel gear 32 a ofthe rotation shaft 32 with the bevel gear is secured to the rotationshaft 32 and meshed with the bevel gear 31, so that the bevel gear 32 ais rotated forwardly/reversely together with the rotation shaft 32, bythe forward/reverse rotation of the bevel gear 31.

In the following description, functions of this rotating actuator 2 afulfilled under the control of the control computer 101 will bediscussed.

Force to be exerted on the bevel gear 31 of the rotating actuator 2 a isdetermined by the magnitude of the generated force of the gas cylinder17 and the amount of inclination of the transmission plate 15 b. Thatis, when the force generated by the gas cylinder 17 (generated force) isexerted upward in FIG. 2A, the force (generated force) is transmitted tothe piston 18, a disc-shaped plate member 19 b, the ball screw nuts 20 ato 20 d secured to positions that are rotation-symmetrical with oneanother relative to the center of the plate member 19 b (morespecifically, at positions at every 90 degrees on the same circumferencearound the center of the plate member 19 b), the threaded shafts 23 a to23 d of the ball screw mechanisms 21 a to 21 d disposed in associationwith the ball screw nuts 20 a to 20 d, and the transmission plate 15 b,so as to press the transmission plate 15 b against the rod-shapedprotrusion 14 c. At this time, in the case where the transmission plate15 b is kept in the horizontal state as shown in FIG. 2A, the generatedforce of the gas cylinder 17 is transmitted to the frame 12 b throughthe rod-shaped protrusion 14 c, the bevel gear 31, and the supportingrod 16, and is kept in a balanced state. On the other hand, in the casewhere the transmission plate 15 b is in an inclined state from thehorizontal state as shown in FIG. 2D (for example, an inclined statediagonally downward to the left), upon transmission of force from thetransmission plate 15 b to the rod-shaped protrusion 14 c, a force in acircumferential direction is exerted at the contact point between thetransmission plate 15 b and the rod-shaped protrusion 14 c, that is, atorque is exerted clockwise around the Z-axis onto the bevel gear 31. Atorque that is exerted counterclockwise around the Z-axis on thetransmission plate 15 b as a reaction can be supported by the supportingrod 16. Moreover, in the case of an inclined state in a directionreverse to that of FIG. 2D (inclined state diagonally downward to theright), a torque is exerted counterclockwise around the Z-axis on thebevel gear 31, with a torque that is exerted clockwise around the Z-axison the transmission plate 15 b as a reaction being supported by thesupporting rod 16. In the case of a statical state with losses due tosliding and the like being ignored, the torque exerted clockwise on thebevel gear 31 in FIG. 2D is represented by a product of the generatedforce of the gas cylinder 17 and the tangent to an angular change of thetransmission plate 15 b from the horizontal state to the inclined state.However, the angular change mentioned here refers to the angular changearound the perpendicular from the contact point between the transmissionplate 15 b and the rod-shaped protrusion 14 c to the rotation shaft ofthe bevel gear 31. Based upon this, by driving the motors 22 a to 22 dso as to set the transmission plate 15 b by the amount of inclination(an inclination angle) corresponding to the magnitude of a force to bedesirably outputted by the control computer 101, the force control ofthe rotating actuator 2 a can be carried out.

Even upon disturbance within a high-frequency band that cannot becontrolled by the control computer 101, since the flexibility ismaintained by the elasticity of the gas cylinder 17, the rotatingactuator 2 a can be a flexible actuator that is safe against contact.

In the case where, in FIG. 2D, the rotating actuator 2 a is in such astate as to allow the bevel gear 31 to rotate clockwise around theZ-axis, the rotating actuator 2 a shall be carrying out a work to theoutside of the rotating actuator 2 a. That is, in the case where thecontrol computer 101 causes the motors 22 a to 22 d to stop fromdriving, as the bevel gear 31 is rotated clockwise around the Z-axis,the plate member 19 b is moved upward in FIG. 2D. At this time, therotating actuator 2 a carries out a work to the outside of the rotatingactuator 2 a with the potential energy that the gas cylinder 17 haslost.

In contrast, in the case where the rotating actuator 2 a is in such astate that the bevel gear 31 is rotated counterclockwise around theZ-axis, the rotating actuator 2 a is subjected to a work from theoutside of the rotating actuator 2 a. That is, in the case where thecontrol computer 101 causes the motors 22 a to 22 d to stand still, asthe bevel gear 31 is rotated counterclockwise around the Z-axis, theplate member 19 b is moved downward in FIG. 2D, so that, by the workdone on the rotating actuator 2 a from the outside of the rotatingactuator 2 a, potential energy is stored in the gas cylinder 17.

In this manner, the rotating actuator 2 a not only carries out a work tothe outside of the rotating actuator 2 a but also carries out aregeneration operation of accumulating energy in the rotating actuator 2a by the work from the outside of the rotating actuator 2 a. Therefore,in comparison with an actuator that is unable to carry out aregeneration operation, the rotating actuator 2 a of the secondembodiment makes it possible to improve its operation efficiency.

Moreover, since the driving force of the rotating actuator 2 a iscontrolled by the amount of inclination of the transmission plate 15 b,it becomes possible to obtain high output by releasing the potentialenergy in the gas cylinder 17 in a short period of time. To replenishpotential energy in the gas cylinder 17, the ball screw mechanisms 21 ato 21 d may be operated by the control computer 101 so that the platemember 19 b is pressed down. In the case where there is a greatdifference between the peak power required of the output of the rotatingactuator 2 a and the average power thereof, since replenishment for thepotential energy released for a short period of time may be carried outby taking sufficient time, the power required for the motors 22 a to 22d may be at a low level in comparison with the peak power. Moreover,since the pressing-down operation of the plate member 19 b is carriedout by the ball screw mechanisms 21 a to 21 d under the control of thecontrol computer 101 in cooperation with one another, it is possible toreduce the power required for each of the motors 22 a to 22 d.

In the following description, the case where the driving torque of therotating actuator 2 a is changed will be discussed. In the secondembodiment, four ball screw mechanisms indicated by the referencenumerals 21 a to 21 d are used as the ball screw mechanism. Since thetransmission plate 15 b is pressed against the rod-shaped protrusions 14c having a fixed length, the transmission plate 15 b is moved with threedegrees of freedom, that is, the displacement in the Z-axis direction,the rotation around the X-axis, and the rotation around the Y-axis,relative to the supporting rod 16. For this reason, the minimum numberof the ball screw mechanisms required is three. However, as shown inFIG. 2D, in the case where the threaded shafts 23 b and 23 d are locatedat positions in the same Y direction as that of the rod-shapedprotrusion 14 c, the generated force of the gas cylinder 17 can besupported by the ball screw mechanisms 21 b and 21 d. For this reason,with the ball screw mechanisms 21 a and 21 c being not influenced by thegenerated force of the gas cylinder 17, the angle of the transmissionplate 15 b can be changed around the X-axis only by the ball screwmechanisms 21 b and 21 d, so that it is possible to change the drivingtorque of the rotating actuator 2 a easily. In addition, in the casewhere only the angle of the transmission plate 15 b is changed, nopositional changes are required with the ball screw mechanisms 21 b and21 d. Therefore, it is only necessary to hold the transmission plate 15b. To dispose the ball screw mechanisms circumferentially in such aredundant manner is desirable because the above state is obtained atmore points. Moreover, to dispose the ball screw mechanismscircumferentially at equal intervals makes it possible to distribute theabove states periodically without causing deviations due to the rotationangle of the bevel gear 31. For this reason, the target expansion orcontraction of each of the ball screw mechanisms (in other words, theadjusting amount of the distance between the plate member 19 a and thetransmission plate 15 a in the moving direction of the ball screw nuts20 a to 20 j in the vertical direction) can be easily calculated, and itis thus possible to eliminate a load to be applied to a specific ballscrew mechanism and consequently to desirably improve thecontrollability of the entire device.

Moreover, in the second embodiment, as shown in FIG. 2F in an enlargedmanner, the transmission plate 15 b is formed into a shape with stepswith its center portion 15 r having a recessed shape relative to itsouter peripheral portion 15 s, and the face (upper face of the centerportion 15 r) with which the rod-shaped protrusion 14 c is made incontact and the face (lower face of the outer peripheral portion 15 s)with which the threaded shafts 23 a to 23 d are made in contact aredesigned to be located on the same plane (substantially on the sameplane). In contrast, in the case of a transmission plate without a step,for example, when the amount of inclination of the transmission plate 15b is changed from the state shown in FIG. 2A, the distance in thevertical direction between the contact point of the transmission plate15 b with the rod-shaped protrusion 14 c and the contact points of thetransmission plate 15 b with the threaded shafts 23 b and 23 d ischanged affected by the thickness of the transmission plate. For thisreason, it becomes necessary to lower the plate member 19 b accordingly,with the result that in order to change the amount of inclination,additional energy corresponding to the increase in potential energy isrequired. Therefore, the transmission plate 15 b is formed into theshape with steps as shown in the second embodiment with the contactpoint of the transmission plate 15 b with the rod-shaped protrusion 14 cand the contact points of the transmission plate 15 b with the threadedshafts 23 b and 23 d being located on the same plane (substantially onthe same plane), which is desirable because this structure can eliminateinfluences from the thickness of the transmission plate 15 b.

Meanwhile, as shown in FIG. 2E as a modification of the secondembodiment of the present invention, the transmission plate 15 b may beformed as a flat-plate transmission plate 15 c without a step, and acircumference that can be taken by the contact point between therod-shaped protrusion 14 c and the transmission plate 15 c and acircumference in which the contact points between the threaded shafts 23a to 23 d and the transmission plate 15 c are included may form the samecircumference that is only reciprocatingly shifted in the Z-axisdirection. That is, as shown in FIG. 2E, this structure is characterizedin that the contact point between the rod-shaped protrusion 14 c servingas one example of the protruding member and the transmission plate 15 cserving as one example of the transmission member includes the contactpoint between the ball screw mechanism serving as one example of thecoupling mechanism and the transmission plate 15 c or the rotationcenter of the coupling portion thereof, and is located substantially onthe same plane as the side face of an elliptic column having a height inthe displacement direction of the plate member 19 b serving as oneexample of the displacement member. With this structure, for example, inrotating the transmission plate 15 c around the X-axis in FIG. 2E, thegenerated force of the gas cylinder 17 is supported by the ball screwmechanism 21 c. For this reason, although there are influences caused bythe thickness of the transmission plate 15 c, the work to be done by theball screw mechanism 21 a can be reduced. The transmission plate 15 c isalso allowed to function as one example of a swinging plate or aswinging member.

In the second embodiment also, the ball screw mechanisms are used as thecoupling mechanism; however, the structure of the coupling mechanism isnot limited to this, and any combination of conventional techniques maybe used as long as the same functions are achieved.

Moreover, FIG. 6 shows a structural example of a joint-driving unit inwhich the rotating actuator 2 a of the second embodiment is used. An arm54 b is disposed above the rotating actuator 2 a, and the arm 54 b isdirectly secured to the rotation shaft 32 of the rotating actuator 2 a.

With this arrangement, when the rotating actuator 2 a is operated fromthe state shown in FIG. 7A so that, by rotating the rotation shaft 32counterclockwise, the arm 54 b is caused to rotate counterclockwise tobe in a state shown in FIG. 7B. In the same manner, by rotating therotation shaft 32 clockwise, the arm 54 b is also allowed to rotate in areverse direction (that is, clockwise).

By using this structure, it is possible to obtain a joint-driving unitthat has the features of the rotating actuator 2 a of being superior inoperational efficiency in addition to being flexible, and also toachieve a joint-driving unit for a robot arm that is particularlysuitable for domestic applications.

Third Embodiment

FIG. 3A is a cross-sectional view schematically showing a rotatingactuator 2 b serving as one example of a flexible actuator in accordancewith a third embodiment of the present invention. Moreover, FIG. 3B is across-sectional view taken along line A-A of FIG. 3A. The portionshaving the same functions as those of the second embodiment areindicated by the same reference numerals, and overlapping description isnot given. In the flexible actuator of the third embodiment also, theZ-axis in the coordinate axes is defined as upward in the verticaldirection. The X-axis is defined as a direction that is orthogonal tothe Z-axis and penetrates one of side faces of a rectangularparallelepiped box-shaped frame 12 c in the thickness direction, theframe 12 c serving as one example of a base member. Moreover, the Y-axisis defined as a direction that is orthogonal to the Z-axis and X-axisand penetrates a side face that is orthogonally adjacent to the sideface of the rectangular parallelepiped box-shaped frame 12 c.

In the third embodiment, the generated force of the gas cylinder 17 istransmitted not by the pressing force, but by tensile force generated byfour wire mechanisms 42 a to 42 d that serve as one example of thecoupling mechanism. In FIG. 3A, the gas cylinder 17 is secured to amiddle portion of the frame 12 c by four supporting members 41 a to 41 d(for example, struts). Moreover, the generated force of the gas cylinder17 is transmitted to a disc-shaped plate member 19 d which is disposedbelow the gas cylinder 17 inside the frame 12 c and to which the lowerend of the piston 18 is secured. Four wire reels 43 a to 43 d aredisposed on the plate member 19 d so as to have intervals of 90 degreesaround the center of the plate member 19 d, with the respective diameterdirections being set in the X-axis or Y-axis direction. The four wirereels 43 a to 43 d are held by the plate member 19 d through bearingportions or the like so as to freely rotate thereon, and the respectiverotation angles of the wire reels 43 a to 43 d are changed byforward/reverse rotations of the rotation shafts of the motors 44 a to44 d that are driven and controlled by the control computer 101. Oneends of wires 45 a to 45 d are coupled to the wire reels 43 a to 43 d,and the wires 45 a to 45 d are respectively allowed to penetratelower-side spherical members 46 a to 46 d that are held on the platemember 19 d by spherical bearings so as to freely swing thereon, withthe other ends of the wires 45 a to 45 d being coupled to upper-sidespherical members 47 a to 47 d that are held on the disc-shapedtransmission plate 15 d by spherical bearings. That is, when, uponinstruction by the control computer 101, the rotation shafts of themotors 44 a to 44 d are rotated, each of the wire reels 43 a to 43 d isrotated simultaneously so that the lengths of the wires 45 a to 45 d (inother words, the lengths between the upper-side spherical members 47 ato 47 d and the lower-side spherical members 46 a to 46 d, that is, thelength between the transmission plate 15 d and the plate member 19 d)are each changed. The transmission plate 15 d is pressed against aspherical portion of the upper end of a rod-shaped protrusion 14 c,which will be described later, by the generated force of the gascylinder 17 transmitted through the wires 45 a to 45 d. Additionally,the transmission plate 15 d is allowed to also function as one exampleof a swinging plate or a swinging member.

Meanwhile, the transmission plate 15 d is held onto a ring-shaped member33 provided with a shaft portion protruding in the X-axis direction by abearing or the like, so as to rotate freely around the X-axis, and atthe same time, the ring-shaped member 33 is held through a bearing orthe like onto the outer cylinder 26 b provided with a shaft portionprotruding in the Y-axis direction so as to rotate freely around theY-axis. Moreover, the outer cylinder 26 b is held on the supporting rod16 serving as a cylinder-shaped spline shaft secured downward to thecenter of the inner face of the upper face of the frame 12 c, so as tomove reciprocatingly freely only in the Z-axis direction (axialdirection of the supporting rod 16). Furthermore, a rotation shaft 49 isheld onto the supporting rod 16, with the lower end of its rotationshaft portion 49 a being secured onto a rotation disc 48 serving as oneexample of a rotating member, through a bearing portion or the like, soas to rotate freely thereon around the Z-axis in a state where therotation shaft portion 49 a penetrates a through hole 12 z on a centerportion of the cylinder-shaped supporting rod 16 and the upper face ofthe frame 12 c. The rotation output to be given to the rotation disc 48by the rod-shaped protrusion 14 c is taken out of the rotating actuator2 b as rotation output around the Z-axis through the rotation shaftportion 49 a and the disc portion 49 b secured to the upper end thereof.The rotation shaft portion 49 a is formed into a small diameter portionby the through hole 12 z of the frame 12 c, and a large diameter portionhaving a diameter larger than that of the small diameter portion isdisposed outside the through hole 12 z. Therefore, when downward forceis applied to the rotation shaft portion 49 a, the large diameterportion of the rotation shaft portion 49 a is made in contact with theperiphery of the through hole 12 z of the frame 12 c so that the forcecan be received by the frame 12 c.

In the following description, functions of this rotating actuator 2 bthat are fulfilled under the control of the control computer 101 will bediscussed.

Force to be exerted on the rotation shaft 49 of the rotating actuator 2b is determined by the magnitude of generated force of the gas cylinder17 and the amount of inclination of the transmission plate 15 d. Thatis, when the force (generated force) generated by the gas cylinder 17 isexerted downward in FIG. 3A, the force (generated force) is transmittedto the piston 18, the plate member 19 d, the wire reels 43 a to 43 dsecured to the positions that are rotation-symmetrical with one anotherrelative to the center of the plate member 19 d (more specifically, atpositions spaced every 90 degrees on the same circumference around thecenter of the plate member 19 d), the wires 45 a to 45 d, the upper-sidespherical members 47 a to 47 d, and the transmission plate 15 d, so thatthe transmission plate 15 d is pressed against the rod-shaped protrusion14 c. At this time, in the case where the transmission plate 15 d is inthe horizontal state as shown in FIG. 3A, the generated force of the gascylinder 17 is transmitted to the frame 12 c through the rod-shapedprotrusion 14 c, the rotation disc 48, and the rotation shaft 49, and iskept in a balanced state. On the other hand, in the case where thetransmission plate 15 d is in an inclined state from the horizontalstate as shown in FIG. 3C (for example, an inclined state diagonallydownward to the left), upon transmission of force from the transmissionplate 15 d to the rod-shaped protrusion 14 c, a force in acircumferential direction, that is, a torque exerted to the rotationdisc 48 counterclockwise around the Z-axis, is applied to the contactpoint between the transmission plate 15 d and the rod-shaped protrusion14 c. The torque that is exerted clockwise around the Z-axis on thetransmission plate 15 d as a reaction is supported by the supporting rod16. Moreover, in the case of an inclined state in a direction reverse tothat of FIG. 3C (inclined state diagonally downward to the right), atorque that is exerted clockwise around the Z-axis on the rotation disc48, with a torque that is exerted counterclockwise around the Z-axis onthe transmission plate 15 d as a reaction being supported by thesupporting rod 16. In the case of a statical state with losses due tosliding and the like being ignored, this torque exerted clockwise isrepresented by a product of the generated force of the gas cylinder 17and the tangent to an angular change of the transmission plate 15 d fromthe horizontal state to the inclined state. However, the angular changementioned here refers to the angular change around the perpendicularfrom the contact point between the transmission plate 15 d and therod-shaped protrusion 14 c to the rotation shaft portion 49 a of therotation shaft 49. Based upon this, by driving the motors 44 a to 44 dso as to set the transmission plate 15 d by the amount of inclination(an inclination angle) corresponding to the magnitude of a force to bedesirably outputted by the control computer 101, the force control ofthe rotating actuator 2 b can be carried out.

Even upon disturbance within a high-frequency band that cannot becontrolled by the control computer 101, since the flexibility ismaintained by the elasticity of the gas cylinder 17, the rotatingactuator 2 b can be a flexible actuator that is safe against contact.Moreover, in the same manner as in the second embodiment, when therotating actuator 2 b is subjected to a work from the outside thereof,energy regeneration is carried out on the gas cylinder 17. In thefollowing description, the case where the driving torque of the rotatingactuator 2 b is changed will be discussed. In the third embodiment, fourwire mechanisms indicated by the reference numerals 42 a to 42 d areused as the wire mechanism; however, since the transmission plate 15 dis pressed against the rod-shaped protrusion 14 c having a fixed length,the transmission plate 15 d is moved with three degrees of freedom, thatis, the displacement in the Z-axis direction, the rotation around theX-axis, and the rotation around the Y-axis, relative to the supportingrod 16. For this reason, the minimum number of the wire mechanismsrequired is three. However, as shown in FIG. 3A, in the case where thewires 45 a and 45 c are located at positions in the same X direction asthat of the rod-shaped protrusion 14 c, the generated force of the gascylinder 17 can be supported by the wire mechanisms 42 a and 42 c. Forthis reason, with the wire mechanisms 42 b and 42 d being not influencedby the generated force of the gas cylinder 17, the angle of thetransmission plate 15 d can be changed around the Y-axis only by thewire mechanisms 42 a and 42 c, so that it is possible to change thedriving torque of the rotating actuator 2 b easily. In the case whereonly the angle of the transmission plate 15 d is changed, since nopositional changes are required with the wire mechanisms 42 a and 42 c,it is only necessary to hold the transmission plate 15 d. To dispose thewire mechanisms circumferentially in such a redundant manner isdesirable because the above state is obtained at more points. Moreover,to dispose the wire mechanisms circumferentially at equal intervalsmakes it possible to distribute the above states periodically withoutcausing deviations due to the rotation angle of the rotation shaft 49.For this reason, the target amount of expansion or contraction of eachof the wire mechanisms (in other words, the adjusting amount of thedistance between the plate member 19 d and the transmission plate 15 din the moving direction of the wire mechanisms 42 a to 42 d in thevertical direction) can be easily calculated, and it is thus possible toeliminate a load to be applied to a specific wire mechanism andconsequently to desirably improve the controllability of the entiredevice.

Moreover, in the third embodiment, the rotation center of the upper-sidespherical members 47 a to 47 d (one example of the rotation center ofthe coupling portion) is arranged so as to be located on the same plane(substantially on the same plane) as the plane on which the transmissionplate 15 d and the rod-shaped protrusion 14 c are made in contact. Thisstructure is desirably used because it becomes possible to eliminateinfluences from the thickness of the transmission plate 15 d.

In the third embodiment, the wire mechanisms are used as the couplingmechanism; however, the structure of the coupling mechanism is notlimited thereto, and any combination of conventional techniques may beused as long as the same functions are achieved.

While the description has been given by exemplifying the gas cylinder 17as the elastic mechanism, the present invention is not limited thereto,and a spring may be used as long as the same functions are achieved.

By properly combining the arbitrary embodiments of the aforementionedvarious embodiments, the effects possessed by the embodiments can beproduced.

INDUSTRIAL APPLICABILITY

A flexible actuator and a joint-driving unit using the actuator inaccordance with the present invention make it possible to carry outforce control easily with superior operational efficiency, and iseffectively used as an actuator or the like for driving joints of arobot and a joint-driving unit or the like using the actuator.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

1. A flexible actuator capable of carrying out a swinging operation anda rotating operation, comprising: a base member; a rotating member thatis held on the base member so as to rotate freely thereon; adisplacement member that is capable of being displaced in a directionthat is substantially same as a rotation shaft direction of the rotatingmember; an elastic mechanism that is secured to the base member, foraccumulating and releasing elastic energy in accordance with a distanceto the displacement member; a transmission member that is connected tothe displacement member so as to allow the distance relative to thedisplacement member to be adjusted by three or more coupling mechanisms;a protruding member that is provided on the rotating member at aposition off a rotation center of the rotating member in a protrudingmanner to be pressed against the transmission member by force generatedby energy released from the elastic mechanism; and a control device forchanging a relative position and a relative angle between thedisplacement member and the transmission member by controlling anadjusting operation of the distance relative to the coupling mechanisms.2. The flexible actuator according to claim 1, wherein the couplingmechanisms are circumferentially disposed at equal intervals.
 3. Theflexible actuator according to claim 1, wherein a contact point betweenthe protruding member and the transmission member is locatedsubstantially on same plane as a plane including a contact point betweenthe coupling mechanisms and the transmission member or a rotation centerof a coupling portion therebetween.
 4. The flexible actuator accordingto claim 1, wherein the elastic mechanism is a ram cylinder or a singlerod cylinder that allows a fluid to move between pressure chambers ontwo sides of a piston.
 5. The flexible actuator according to claim 1,wherein the coupling mechanisms have a structure with which the distancebetween the displacement member and the transmission member isadjustable substantially in parallel with a displacement direction ofthe displacement member and which is pressed against the transmissionmember by generated force of the elastic mechanism.
 6. A joint-drivingunit driven by the flexible actuator of claim 1.